1. Field of the Invention
This invention generally relates to a method of heat treatment by irradiation, and, in particular, to a method of heat-treating a thin film utilizing irradiation of light. More specifically, the present invention relates to a method for annealing a thin film formed on a substrate so as to provide a desired property to the thin film, such as single crystalline or microcrystalline structure or photoconductive characteristic.
2. Description of the Prior Art
It is well known to deposit a thin film on a support which has a relatively large surface and which is not crystalline in structure and to anneal this thin film by a laser beam, an electron beam, etc., thereby providing a single crystalline structure in the thin film. Such a prior art method allows to form a single crystalline thin film large in surface area, which is expected to contribute to various improvements in such electronics devices as a switching device for driving a liquid crystal display, a switching device for a unity magnification photosensor, and CCD image sensor.
However, in the prior art method, since the thin film deposited on the support does not normally have a desired single crystalline structure and it is often amorphous or polycrystalline, in, structure, the thin film must be annealed to give it desired properties. For this purpose, the thin film is heat-treated to obtain a single crystalline structure, for example. In accordance with the prior art method, in such a case, use is normally made of a laser beam or an electron beam to carry out annealing of the thin film; however, such a beam annealing requires scanning an annealing beam across the large surface area so that there must be provided a control system for beam scanning, and, moreover, such a prior art method is significantly time consuming.